5 ms·

Can forth handle delay execution. Or a conditional where one later parameter never need is not reached. It seems all parameters at least needed to be in first

Can forth handle delay execution. Or a conditional where one later parameter never need is not reached. It seems all parameters at least needed to be in first, say a rough lisp like use case. (Def ExecN func n infinite-series) (ExecN + 10 integer) ... can it be done in forth.

RodgerTheGreat 7y ago
Of course. You can build whatever functional abstractions you like in Forth. Some time ago I did a number of experiments with lazy generators: https://github.com/JohnEarnest/Mako/blob/master/lib/Algorithms/Lazy.fs#L95-L104 https://github.com/JohnEarnest/Mako/blob/master/lib/Algorith... The above dialect uses { } to delimit anonymous inline word definitions. RetroForth has a similar feature, and Factor uses the same syntax for "quotations", which have slightly different semantics but roughly the same meaning.
- ngcc_hk 7y ago
  Thanks. If I start today to learn as I have searched a bit ... it seems to have a dialect retroForth whilst I see a 10 years old recommend swiftforth ... Actually the tutorial that host a forth on js (like clojurescript just self implement). Which path to go? Do not want to learn lisp ended up in scheme.
  - RodgerTheGreat 7y ago
    On desktops I've used gforth[0]. It's rather large and heavyweight, but easy to install and has decent documentation; not a bad starting point. Alternatively, JonesForth[1] is an excellent extensively-commented implementation suitable for reading start-to-finish. [0] https://www.gnu.org/software/gforth/ https://www.gnu.org/software/gforth/ [1] https://github.com/nornagon/jonesforth/blob/master/jonesforth.S https://github.com/nornagon/jonesforth/blob/master/jonesfort...
  - lebuffon 7y ago
    Forth can be a little troublesome in that area. There is a standard language but it is primitive. Extensions for real world problems tend to diverge in syntax. This has lead to a saying: "If you've seen one Forth, you've seen one Forth" :) It's better than in the past with an ISO standard (IMHO) but know that if you change language providers there will be differences for things like external library linking (if available), GUI interaces etc. There are demo versions of commericial systems at: https://www.mpeforth.com/resource-links/downloads/ https://www.mpeforth.com/resource-links/downloads/ https://www.forth.com/download/ https://www.forth.com/download/ And of course a major pass-time in the Forth community is writing your own Forth. There is even a few Forths written in Python. (for instructional purposes only I assume) http://openbookproject.net/py4fun/forth/forth.html http://openbookproject.net/py4fun/forth/forth.html
int_19h 7y ago
Immediate words in Forth are somewhat analogous to macros, and therefore can do this kind of stuff if need be - not evaluating something, or evaluating something several times. Take a look at a sample implementation of IF/ELSE/THEN and DO/LOOP: https://github.com/nornagon/jonesforth/blob/4f853252f715132e7716cbd44e5306cefb6a6fec/jonesforth.f#L118 https://github.com/nornagon/jonesforth/blob/4f853252f715132e... Forth also has anonymous words (:NONAME), so you can dynamically define a computation and pass it around on the stack, and later execute it. I don't think there's any way to clean them up, though (no GC).

RodgerTheGreat 7y ago

Of course. You can build whatever functional abstractions you like in Forth. Some time ago I did a number of experiments with lazy generators: https://github.com/JohnEarnest/Mako/blob/master/lib/Algorithms/Lazy.fs#L95-L104 https://github.com/JohnEarnest/Mako/blob/master/lib/Algorith... The above dialect uses { } to delimit anonymous inline word definitions. RetroForth has a similar feature, and Factor uses the same syntax for "quotations", which have slightly different semantics but roughly the same meaning.

ngcc_hk 7y ago
Thanks. If I start today to learn as I have searched a bit ... it seems to have a dialect retroForth whilst I see a 10 years old recommend swiftforth ... Actually the tutorial that host a forth on js (like clojurescript just self implement). Which path to go? Do not want to learn lisp ended up in scheme.
- RodgerTheGreat 7y ago
  On desktops I've used gforth[0]. It's rather large and heavyweight, but easy to install and has decent documentation; not a bad starting point. Alternatively, JonesForth[1] is an excellent extensively-commented implementation suitable for reading start-to-finish. [0] https://www.gnu.org/software/gforth/ https://www.gnu.org/software/gforth/ [1] https://github.com/nornagon/jonesforth/blob/master/jonesforth.S https://github.com/nornagon/jonesforth/blob/master/jonesfort...
- lebuffon 7y ago
  Forth can be a little troublesome in that area. There is a standard language but it is primitive. Extensions for real world problems tend to diverge in syntax. This has lead to a saying: "If you've seen one Forth, you've seen one Forth" :) It's better than in the past with an ISO standard (IMHO) but know that if you change language providers there will be differences for things like external library linking (if available), GUI interaces etc. There are demo versions of commericial systems at: https://www.mpeforth.com/resource-links/downloads/ https://www.mpeforth.com/resource-links/downloads/ https://www.forth.com/download/ https://www.forth.com/download/ And of course a major pass-time in the Forth community is writing your own Forth. There is even a few Forths written in Python. (for instructional purposes only I assume) http://openbookproject.net/py4fun/forth/forth.html http://openbookproject.net/py4fun/forth/forth.html

int_19h 7y ago

Immediate words in Forth are somewhat analogous to macros, and therefore can do this kind of stuff if need be - not evaluating something, or evaluating something several times. Take a look at a sample implementation of IF/ELSE/THEN and DO/LOOP: https://github.com/nornagon/jonesforth/blob/4f853252f715132e7716cbd44e5306cefb6a6fec/jonesforth.f#L118 https://github.com/nornagon/jonesforth/blob/4f853252f715132e... Forth also has anonymous words (:NONAME), so you can dynamically define a computation and pass it around on the stack, and later execute it. I don't think there's any way to clean them up, though (no GC).